The present invention relates to an apparatus and process for drying wet sludge, particularly industrial waste sludge. The sludge is circulated through the apparatus as it is being dried.
Municipal waste water treatment plants create sewage sludge in large amounts. Also, industrial sludge of any variety is becoming a sensitive environmental concern. Raw sewage received in waste water treatment facilities is treated by various known methods which generate the wet sludge. Industrial sludge is generated from any variety of industrial processes. Thereafter, a problem remains as to how to treat the wet sludge in an environmentally safe, energy efficient, and economical manner. In the past, such sludge has been disposed in many ways such as direct land application of the sludge, composting the sludge, land filling the sludge, ocean filling the sludge, and drying and incinerating the sludge. Wet sludge typically contains inorganic and organic matter, nutrients such as nitrogen, phosphorous, potassium, and traces of various other metals. The sludge may also contain heavy metals and hazardous organics, depending upon the source of the raw sewage or industrial waste that has been treated.
In known methods of treating wet sludge, the sludge is treated to increase the solid content thereof. That is, the sludge is dewatered by gravity, by mechanically dewatering the sludge, or by thermal treatment of the sludge.